It is well known to employ protective laminates to provide an abrasion-resistant surface on substrates that are subject to abrasion damage. Among the many uses for such protective laminates, one which imposes especially stringent requirements is use in the photographic field. Many photographic products are amenable to significant improvement in their performance through use of such abrasion-resistant laminates, for example, photographic color prints, graphic arts films, X-ray films, motion picture films, microfilms and microfiche. Photosensitive elements known in the art as "phototools" have an acute need for the type of protection against abrasion and scratches that can be provided by a protective laminate, and impose especially demanding constraints. Such elements are used, for example, in the preparation of lithographic printing plates and in the utilization of photoresists in the production of printed circuits. The phototool is composed of a support with a high degree of dimensional stability and one or more layers of a photosensitive material, such as a silver halide emulsion, a photopolymer composition or a diazo composition coated on the support. The photosensitive layer has a relatively soft surface and is thereby subject to scratching, abrasion and other damage in use which severely detracts from its capabilities. Moreover, the optical and mechanical requirements are very stringent, so that a useful protective laminate must provide the desired protection without interfering with the ability of the phototool to meet these exacting requirements.
Many attempts have been made heretofore to produce protective laminates that are useful with substrates needing protection against abrasion, scratches and the like, including phototools and other photographic materials, as well as glass, plastics, metals and many types of fragile coatings. Protective laminates particularly intended for use with phototools are described in Fulwiler, U.S. Pat. No. 4,077,830, issued Mar. 7, 1978; while those particularly intended for use with photographic color prints are described in Segel, U.S. Pat. No. 4,378,392 issued Mar. 29, 1983, and Miller, U.S. Pat. No. 4,581,267, issued Apr. 8, 1986. The protective laminates of Eshleman, U.S. Pat. No. 4,337,107 issued June 29, 1982 are described as being useful in the protection of a very wide range of substrates, including photographic elements and many other materials.
While the protective laminates of the prior art are useful in many applications, they suffer from serious deficiencies which have hindered more widespread commercial application. Thus, for example, they are frequently too thick and thereby subject to causing optical distortion to too great an extent to be successfully employed in the photographic field. Another common problem is their ability to provide a protective surface with as high a degree of resistance to abrasion and scratching as is needed. Yet another concern is the tendency of protective laminates to cause excessive curling of the photographic element to which they are applied. A still further problem is the great difficulty in manufacturing a protective laminate which is extremely thin, and in applying such laminate in a wrinkle-free state, because of the many difficulties that arise in conveying and handling extremely thin web materials.
It is toward the objectives of providing a new and improved protective laminate which overcomes the deficiencies of the prior art, and of providing a commercially practical method for the manufacture of such laminate, that the present invention is directed.